1. Field of the Invention
The invention relates generally to the field of printers, and more specifically to selective dot matrix printers.
2. Description of the Prior Art
A printer employing the principles of the hereindisclosed invention forms a part of a ribbonless check endorser. Such an endorser, an example of which is described in U.S. Pat. application Ser. No. 650,707, filed Jan. 20, 1976 and assigned to the assignee of the present application, is used to print selected information such as a date, a code number or the like, onto a face (normally the rear face) of the check. Prior art devices have generally used an ink-bearing ribbon impressed between a print head and a document supported on a platen to effectuate printing. The use of the ribbon, however, necessitates the provision of a bulky ribbon drive and reverse mechanism, and the ribbon itself must be periodically changed, which can be a time-consuming operation. Other devices have included ink jet printers, the nozzles of which can become clogged and must be periodically cleaned, and the ink spray itself can have undesirable aspects.
The endorser disclosed in the above-referenced patent application Ser. No. 650,707, prints selective information onto the check by providing an inked rotatable cylindrical platen adapted to support the document, printing taking place on the face towards the platen. Ink is transferred to the document from the platen responsive to the impact. The documents travel through the printer when being printed upon at the same speed as the peripheral velocity of the rotating platen, the speed of the document past the print station being limited by a speed control roller cooperating with a pressure roller, with the documents being pinched therebetween. Because it is sometimes desired to avoid printing on a check, gaps are provided in the platen and the speed control roller to allow the documents to travel therepast without engaging the slower-rotating platen wheel. However, during printing the information to be printed on the document may be of sufficient length that the gap in the rotating platen is encountered. In such a case a gap also occurs in the printing on the document.